Modern airbag systems generally employ a so-called “seamless design” according to which the position of an airbag cannot be easily recognized by a vehicle occupant. The seamless design allows the vehicle occupant to unintentionally place an object, such as map, mobile phone or the like, on a lid or cover part of the front airbag module, which is provided or formed as an integral part of the vehicle instrument panel. When the front airbag module is activated to deploy an airbag at a collision, the object on the cover part will hinder proper deployment of the airbag and may strike and injure an occupant of the front passenger seat disposed in front of the front airbag module.
To deal with this problem, a front airbag system disclosed in Japanese Patent Application Laid-Open Publication No. 3-248946 (JP 3248946 A) includes, as shown in FIG. 10 hereof, a detection device 200 mounted on a front side of an instrument panel 201 for undertaking detection of an object which is in contact with a part of the instrument panel 201 forming a lid or cover part 202 of a front airbag module 203. The detecting device 200 consists of a touch sensor formed by a pressure-sensitive resistance sheet disposed below a skin layer 201a of the instrument panel 201. The touch sensor (detecting device) 200 is electrically connected to a control unit (not shown) of the front airbag module 203 for ensuring proper deployment control of an airbag 204 of the front airbag module 203. More particularly, when the touch sensor (detecting device) 200 detects an occupant of the front passenger seat or an object, which is in contact with the cover part region 202 of the instrument panel 201 from the outside, this sensor 200 issues a detection signal to suppress deployment of the airbag 204.
However, the touch sensor 200 assembled in the instrument panel 201 increases the manufacturing cost. Furthermore, due to difficulties in adjusting the detection sensitivity to accommodate various objects of different weights, the touch sensor 200 is likely to involve detection errors, which will allow improper deployment of the airbag 204 tending to cause an injury of the occupant of the front passenger seat.